Who would have believed it? When George Bush arrives in Jerusalem today to salvage something from the wreckage of his attempt to impose a new pax Americana on the Middle East, there will at least be one ray of sunshine in an otherwise grim presidential vista. Iran may be resurgent, Hizbullah unbroken, the prospect of an Israel-Palestine peace settlement more remote than ever. But, as far as the US administration is concerned, things are at last coming good in Iraq. Its people are "reclaiming a normal society", Bush has declared, a theme echoed enthusiastically across the US and wider western media. American casualties are down, economic growth is up, refugees are returning home, and people can once again walk the streets of Baghdad in safety, the story goes.

"We are out of the woods," Muwaffaq al-Rubaie, the Iraqi government's national security adviser, insisted last month. And however such claims are regarded in Iraq, they are certainly having an impact on the US presidential elections. The Iraq war is still top of American voters' concerns, but it now jostles with the economy, immigration and healthcare and, while a clear majority want troops withdrawn, a record 40% believe the past year's troop surge is making things better. The result is that the leading Democratic candidates are hedging their bets on troop withdrawal - Barack Obama would keep trainers and special forces, Hillary Clinton is only committed to pulling most troops out by 2013. Meanwhile, the glad tidings from Iraq means pro-war Republicans are once again in with a fighting chance.

The one part of this tale that is true is that the level of violence has dropped sharply in the past three months, both involving Iraqis, and US and British occupation troops. The monthly average of US soldiers killed between October and December was 33, compared with 110 in April to June, and the number of Iraqi civilians reported killed in December was 902, according to Iraq Body Count, compared with 2,731 in May. Any reduction in the suffering of Iraqis in particular, who have certainly endured hundreds of thousands of deaths as a result of the invasion of their country, must obviously be welcome. But if that dip in violence is misinterpreted as reflecting the beginning of a successful stabilisation and reduces the pressure to end the occupation, it will only prolong that agony into the future.

The fact is that 2007 was the deadliest year for US troops, with 901 killed; and the second bloodiest for Iraq as a whole, with at least 22,586 civilian deaths. The level of resistance attacks on US forces is still running at 2,000 a month, and the level of violence is back to roughly where it was in 2004-05 - seen as disastrous at the time. The reasons for that drop are mostly not disputed. The first is the creation of "awakening councils", in effect US-backed Sunni militias, to police areas that have been at the heart of the resistance campaign.

Then there is the six-month ceasefire called by Moqtada al-Sadr's anti-occupation Mahdi army, the most powerful Shia militia in the country. And lastly, there has been the impact of the surge in US troop numbers and the change of tactics orchestrated by its architect, General Petraeus, including the carving up of cities such as Baghdad into ethnically cleansed security zones behind Israeli-style walls, barriers and checkpoints. Iraqis also report that US troops have sharply reduced their patrols and operations in the last couple of months in Baghdad and elsewhere, with fewer clashes as a result.

But already, the upsurge in bombings, assassinations and attacks on US forces in the last couple of weeks - including the first killing of American troops by an Iraqi soldier - should be a warning to those now talking up the success of the surge. Here are four reasons why the lull in violence is highly unlikely to hold. First, the occupation-funded awakening councils, which are now getting on for 80,000-strong, are an unstable mishmash of groups with different agendas, created in the teeth of opposition from the supposedly sovereign Iraqi government, which have already been drawn into sectarian clashes with Shia militias. To solve one problem, the US has created another.

Second, the surge was only ever a temporary fix, and US troop numbers are already being reduced. Third, violence has been increasing in Shia areas and is likely to continue to do so, both as militias vie for power and as they come into conflict with US forces now tilting towards Sunni interests - or as a result of the clash between the US and Iran. But perhaps most important, there hasn't been the slightest move to a political settlement for which the surge was meant to buy time. The government barely exists, parliament rarely manages a quorum, and there has been no change in the fundamental issue which drives armed resistance: the foreign occupation of the country against the will of its people.

The reality of the surge is this: the number of people displaced from their homes has quadrupled to over 2 million, and detention without trial has risen dramatically (the US alone holds 25,000 prisoners). Another 2 million have fled the country since the occupation began - and about 30,000 have returned, mostly because of lack of cash and visa restrictions. In oil-rich Iraq, electricity is now available in Baghdad for only eight hours a day, half the level before the invasion; unemployment is over 60%; food rations are being cut; corruption is rampant; and 43% of the population now lives on less than a dollar a day.

The surge has bought time for the US but achieved nothing to prepare the way for an end to the occupation. On the contrary, Bush recently signed an agreement with Prime Minister Nouri al-Maliki for a long-term presence in the country. On Monday, a spokesman for what is regarded as the largest Sunni-based resistance group in Iraq, the Islamic Army, rejected any cooperation with the awakening councils and pledged to "resist the US forces as long as they are in Iraq". Meanwhile, focus-group surveys carried out for Petraeus in five Iraqi cities last month found that all sectarian and ethnic groups believe the US invasion is the primary cause of violence in the country and regard the withdrawal of all occupying forces as the key to national reconciliation. Those who preach democracy for Iraq should listen to its people.